Connecting soil characteristics to edge-of-field water quality in Ohio

Authors: Osterholz, William - Will; SCHWAB, ELIZABETH - The Ohio State University; DUNCAN, EMILY - Los Angeles Regional Water Control Board; Smith, Douglas; King, Kevin

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2021
Publication Date: 11/16/2021
Citation: Osterholz, W.R., Schwab, E.R., Duncan, E.W., Smith, D.R., King, K.W. 2021. Connecting soil characteristics to edge-of-field water quality in Ohio. Journal of Environmental Quality. Article 20308. https://doi.org/10.1002/jeq2.20308.
DOI: https://doi.org/10.1002/jeq2.20308

Interpretive Summary: Soil health improvement is growing in popularity as a goal of cropland management, but the relationships of soil health with water quality are not well studied. This analysis utilized on a network of fields in Ohio that were monitored for water quality by comparing a wide array of soil chemical, physical, and biological properties to water quality impacts including losses of phosphorus and nitrate through surface runoff and subsurface tile drains. Across these fields we found that higher soil phosphorus concentrations tended to be associated with larger phosphorus losses. Additionally, soils with higher water extractable carbon and nitrogen were associated with higher nitrate losses through tile drains. Few other soil properties were found to be consistently related to water quality outcomes. This work suggests that some soil health indicators were associated with greater nutrient losses, while others had little influence on water quality. Further research that controls for management effects and that explores additional soil health indicators is needed to confirm these initial findings regarding relationships between soil health and water quality.

Technical Abstract: Soil health and water quality improvement are major goals of sustainable agricultural management systems, yet the connections between soil health and water quality impacts remain unclear. In this study we conducted an initial exploratory assessment of the relationships between soil chemical, physical, and biological properties and edge-of-field water quality across a network of fields in Ohio, USA. Fields were monitored for discharge, dissolved reactive P (DRP), total P (TP), and nitrate losses associated with precipitation events via surface runoff and tile drainage. Agronomic soil tests and a suite of soil health indicators were measured, then predictive relationships between the field average soil properties and tile drainage and surface runoff discharge and DRP, TP, and nitrate loads were explored with random forest and multiple linear regression approaches. Among the soil health indicators, water extractable C and N were consistently found to be positively related to tile nitrate loads, but other soil health indicators had little or inconsistent importance for water quality impacts. Several other soil properties were important predictors, particularly soil P pools for surface and tile DRP and TP losses as well as Mehlich-3 extractable Fe and Al for surface and tile discharge. Thus, we did not observe strong evidence that soil health was associated with improved edge-of-field water quality across the edge-of-field monitoring network. However, additional studies are needed to definitively test the relationships between a broader array of soil health metrics and water quality outcomes.